CRANE. | Pumping Machinery. 315 
used, except in the sump, being located in abandoned or air 
shafts, there is little or no objection to their use in this dis- 
trict. 
DriREcT-ACTING PLUNGER AND Piston Pumps.— Most of the 
steam pumps used are direct-acting force pumps, and are 
plunger or piston pumps, depending on whether they are to 
work at high or low pressure, and are generally of the du- 
plex type. 
Steam sinking pumps, suspended in the shaft by chains or 
hooks, are becoming of common occurrence. 
As the height to which the mine waters have to be lifted 
in order to be expelled from the mine is comparatively slight, 
the problem of pumping has as yet presented no serious or 
difficult features; therefore, any form of steam pump which 
does good work at from 250 to 300 feet can be relied upon to 
work satisfactorily in this district, except where acid waters 
are prevalent. 
THe Rotary Pump.—The principal form of rotary pump in 
this district is the Miracle pump. Plate XLV. The essential 
features of this pump are: First, a double cylinder, in which 
rotate two cog wheels with \-shaped cogs, which fit closely to 
the side of the cylinder, the cogs of which fit into each other 
closely, making practically a water-tight connection, yet move 
smoothly and with little friction; second, the shafts bearing 
the cogs are driven either by belt or by a vertical shaft. One 
of the shafts may be called the drive shaft, which causes the 
other to rotate by two small cog wheels, one upon either shaft. 
For sinking purposes or for a shaft pump, the vertical form 
is employed, in which case the power shaft reaches from the 
surface to the pump below and is usually driven by a belt 
from the hoister engine. The horizontal form of rotary 
pump, which is used either on the surface or in some part 
of the worked-out portion of the mine, is usually driven by a 
belt ; if above, by a belt from the hoister engine ; if below, by 
a small stationary engine placed near the pump. 
It is possible to employ the vertical form of rotary pump 
in any part of the mine proper, by drilling a hole through 
the roof and introducing the shaft through this hole from 
21—vili 
